Patent Document 1 discloses a battery pack that is configured to accommodate battery cells in a sealed case. The battery pack is configured to release the internal pressure of the sealed case.
FIG. 7 illustrates the battery case disclosed in Patent Document 1. The battery case has an opening 101, which is sealed by a sealing plate 102. The sealing plate 102 is fixed to the battery case with fastening members 103. In this configuration, when there is an abnormality in any of the batteries in the battery case and that battery discharges gas, the internal pressure of the battery case increases. This deforms the sealing plate 102 away from the battery case. Then, a clearance is formed between the sealing plate 102 and the battery case, and the gas discharged by the battery is discharged to the outside of the battery case through the clearance. This releases the internal pressure of the battery case.
However, if the deformation of the sealing plate 102 reaches the part that is fixed to the battery case with the fastening members 103, the following drawbacks are caused. That is, the deformation of the sealing plate 102 concentrates stress on the fastening members 103. This can cause the fastening members 103 to come off the battery case so that the sealing plate 102 may come off the battery case.